What condition often leads to the formation of radiation fog?

The formation of radiation fog is primarily associated with ground cooling due to terrestrial radiation. This phenomenon occurs during the night when the ground loses heat rapidly through radiation. As the temperature of the ground decreases, it chills the air directly above it. If the air cools to its dew point—meaning it reaches saturation—the moisture in the air condenses into tiny water droplets, creating fog. This type of fog typically forms in calm, clear nights when there is little to no wind to mix the air, allowing the air closest to the ground to cool efficiently. Understanding this process helps clarify why this option accurately describes the conditions leading to radiation fog formation.